Valve Seat: Service and Repair

Valve Seats, Reworking

• If a perfect contact pattern is not achieved by grinding the valve seats, rework the valve seats.

Special tools, testers and auxiliary items required

• Depth gauge

• Valve seat refacing tool

• When repairing engines with leaking valves, it is not sufficient to rework or replace valve seats and valves. It is particularly important to check valve guides for wear on engines with higher mileage performance. Refer to => [ Valve Guides, Checking ] Testing and Inspection.

• Only reface valve seats enough until a perfect contact pattern is obtained.

• Before refacing, determine maximum refacing dimension.

• If the reworking dimension is exceeded, the function of the hydraulic lifters can no longer be guaranteed and therefore the cylinder head must be replaced.

Determining maximum allowable reworking dimension

- Insert valve and press it firmly against the valve seat.

• If the valve is to be replaced as part of a repair, use a new valve for the calculation.

- Measure distance - a - between end of valve stem and the upper cylinder head surface with a depth gauge.





- Calculate the maximum allowable reworking dimension from the measured distance and minimum dimension.





Measured distance minus minimum dimension = Max. permissible reworking dimension.





• If the maximum allowed reworking dimension is 0 mm or less than 0 mm, repeat measurement using new valve. If measurement result is still 0 mm or less than 0 mm, replace cylinder head.

Reworking intake valve seat





a Dia. 26.2 mm
b 1.5 to 1.8 mm
Z Cylinder head lower edge
alpha 45° valve seat angle
β 30° upper correction angle
γ 60° lower correction angle

• Calculating maximum allowable reworking dimension.

Reworking exhaust valve seat





a Dia. 29.0 mm
b 1.8 mm
Z Cylinder head lower edge
alpha 45° valve seat angle
β 30° upper correction angle
γ 60° lower correction angle

• Calculating maximum allowable reworking dimension.